This is a comprehensive knowledgebase on the 'need to know' issues when making your own IR-Pen. Covering basic eletronic principles and desirable IR-Led qualities. How you design and construct your pen is totally up to you. I have linked to my instructional videos as the bottom, but I also suggest you Google IR-Pen and read the Forum posts to find many other concepts.

Lesson 2: Use a resistorThey saves blowing IR-LED's and prolongs the life of diode and battery. They only cost about 15 cents.To calculate the required resistor you need the Maximum Source Voltage, Diode Typical Forward Voltage and Diode Forward Current. Smart people (not me) will use Ohm's Law, the rest just use an online calculator like http://led.linear1.org/1led.wiz.Example: Vishay 6400 Typical Forward Voltage = 1.35v 2x 1.2v Rechargeable AAA/AA Batteries = 2.4v Diode Forward Current = 100ma Put this data into the online calculator and you will get a 12ohm Resistor.(You use the Maximum Source Voltage and the Typical Diode Forward Voltage to ensure Diode is adequately protected)

This is main data from Vishay's Datasheet for the TSAL6400 used to calculate the above. I have circled the necessary information. The Power Source data will need to come from its manufacturer too.See below for full datasheet's

Lesson 3: IR LED's are polarity sensitiveThe long connector (anode) is positive and the short connector (cathode) is negative. If you look carefully at the LED the cathode is the flat piece inside.

Lesson 4: Get a wide viewing angle IR-LEDI have tried a few 30 degree and a really strong 25 degree LED and all work best when directed into the wiimote, rather than the whiteboard as I intend to use it (thus not very good at angles). (Vishay 6400 seems to be the way).Viewing angle graphs like this can usually be found on the IR-LED Datasheet (this is random example and not related to the IR-LED pics below)

Lesson 7: How do I know my IR-LED works???Easy look at it through your mobile phone camera (cool little trick). You will be able to see the importance of the viewing angle, with the 25 degree from the side it looks like a dim light in the distance, front on it is very bright. (Remember 25 degree's means 12.5 degree's either side of 0 degree's. Thus not very wide, even over a long distance)

These photo's are from a camera phone of a: 25 Degree viewing angle, 1.2v AAA, 12ohms Resistor, 100ma LED. Note you can "see" the light and how difficult it will be for an IR sensor to detect the light from angles greater than 35 degree's, but also how strong it is at 0 degree's.

LED @ 90 degree's

LED @ 20 degree's

LED @ 0 degree's

Lesson 8: ScematicA basic IR-Pen scematic:

Lesson 9: Read all the instructions & feedbackI left this to last knowing most people like me won't even read the first lesson, until they get totally stuck or until they finally got it to work and then read the instructions to check they did it right!benpaddlejonesIRPENmach1 failed because I only read the ingredients list (2x AAA batteries) but didn't read the complete instructions that said I should only use 1 of the 2 batteries! benpaddlejonesIRPENmach2: failed because I reverse wired it and assumed it was a busted LED! benpaddlejonesIRPENmach3: works (mostly thanks to the really smart dude at www.altronics.com.au) but only if it is directed at the wiimote because of its small viewing angle! benpaddlejonesIRPENmach4: Works AWESOME see my video:http://www.wiimoteproject.com/videos/enhancing-teaching-learning-with-the-wiimote-interactive-whiteboard-t983.0.html

Thanks for the excellent tutorial! One question though: what about the 'radiant intensity' of an IR led. Does that play any role in selecting the most suitable IR led?

I could be a little (or a lot) out of my depth but:

My understanding is Radient Intensity is a measure of light emmited over a period of time. Given the Wiimote locks for Blobs either at the IR-LED or reflected on the whitebaord this is not overlly relievent. It is also a function of the forward current so that is a suitable measure of strength for us nOOb's.

I welcome correction and advice from any Electronic/Physic Guru's though.

I am probably the uber-est n00b when it comes to this kind of electronics stuff so I'm not quite sure what to do. I thought I'd try out this wiimote whiteboard thing just to learn something and have a little fun at the same time I have bought some Vishay TSAL 6400 LED's so far... and I have no idea what to do. I did not buy resistors because I'm not sure what to get.

I understand that the LED's forward voltage is 1.35v and a max voltage of 1.6v? So if the voltage of a battery is 1.5v will it work without any resistors?

I'm sorry for asking what are probably some really stupid questions but I would love to get this working. I appreciate anyone that takes the time to answer me

Thanks for the excellent tutorial! One question though: what about the 'radiant intensity' of an IR led. Does that play any role in selecting the most suitable IR led?

I could be a little (or a lot) out of my depth but:

My understanding is Radient Intensity is a measure of light emmited over a period of time. Given the Wiimote locks for Blobs either at the IR-LED or reflected on the whitebaord this is not overlly relievent. It is also a function of the forward current so that is a suitable measure of strength for us nOOb's.

I welcome correction and advice from any Electronic/Physic Guru's though.

benpaddlejones

See http://www.vishay.com/docs/49495/sg2123.pdfI see that the wider the angle the lower the radient intensity. The difference between the 5300 and the 6400 reveals that the 5300 will be brighter as is mentioned somewhere in this forum.